Field of the Invention
The invention relates to an insulation problem detection apparatus and an insulation problem detection method.
Description of the Background Art
Vehicles such as hybrid vehicles and electric vehicles that have been widespread these days include a power supply that supplies power to a motor that is a power source. The power supply includes an assembled battery made by a plurality of stacked storage cells. A voltage output from the power supply is supplied to the motor after the voltage is boosted by a voltage converter.
There is a technology that detects an insulation problem of a vehicle in the foregoing configuration based on a voltage at which a flying capacitor is charged, for example, having the power supply, the flying capacitor, an insulation resistance of a vehicle and a vehicle body ground connected in series. Moreover, when detecting the insulation problem, the technology charges the flying capacitor by a total voltage of the power supply, having the power supply and the flying capacitor connected in series, and then uses a total voltage of battery supply measured based on the voltage.
However, the foregoing technology has a problem of low accuracy of the measured voltage of the charged flying capacitor. For example, the voltage boosted by the voltage converter fluctuates because measurement time points are different. Therefore, different reverse charge occurs whenever the flying capacitor is charged so that in some cases, accurate insulation resistance cannot be measured. Moreover, for example, since the time points of measurement are different, measured total voltages of the power supply are different, and thus there is a case where accuracy of the total voltage of the power supply may be decreased. In other words, if the foregoing technology is used, because the accuracy of the measured voltage of the flying capacitor is low, accuracy of the measured insulation resistance and accuracy of the measured total voltage of the power supply of the vehicle are also low. Accordingly, there is a problem that the insulation problem of the vehicle cannot be detected accurately.